Coatings and paints are routinely used to beautify and protect substrates. The most simple coatings and paints are made of a polymer (the binder) in a solvent (the vehicle), which is commonly called a lacquer. Paints and coatings modify the appearance of an object by adding color, gloss, or texture, and by blending with or differentiating from a surrounding environment. For example, a surface that is highly light scattering can be made glossy by the application of a paint that has a high gloss. Conversely, a glossy surface can be made to appear flat. Thus, the painted surface is hidden, altered, and ultimately changed in some manner by the presence of the coating. In addition, paints also protect the surface from the surrounding elements and prevent or reduce the corrosive process.
Paints and coatings, while protecting the substrate from external environment, can themselves get dirty over time. The dirt can dull the coating by increasing the light scattering or by modifying the color of the coating. Dirt can also affect a paint's durability. Thus, it is desirable to have coatings with a hydrophilic surface and self-cleaning properties. A hydrophilic surface would allow water to spread out in a thin layer, sweeping dirt off the surface as the water thins out and trickles away. This type of “self-cleaning” behavior is advantageous to an exterior paint, as it keeps the coating clean without requiring extensive cleaning by the customer. A hydrophilic surface would allow water to sheathe over the surface and either solvate or even carry away the dirt molecules.